Tennis shops near Wimbledon have done a brisk trade in replicas of Rafael Nadal's recent vivid green match-winning shirt, testament, perhaps, to his status as a real threat to Roger Federer's dominance at the championships.

Many former and current players have tipped Nadal, who will revert to the traditional Wimbledon white when the tournament starts today, to break Federer's 59-match grasscourt winning streak, which has brought him five Wimbledon titles in a row.

Nadal crushed the world number one in the French Open final two weeks ago, allowing him only four games, and went on to win his first grasscourt title at Queen's a week later to prove he was not master merely of clay.

The 22-year-old Spaniard, runner-up to Federer at Wimbledon the last two years, is not talking up his chances, however.

He scoffed at reporters last weekend who suggested Federer might be vulnerable, pointing out the Swiss had just won the Halle warm-up tournament.

Third seed Novak Djokovic, forced to pull out against Nadal in the semi-finals last year with blisters but who has since won the Australian Open, said:

"Roger is still the number one player in the world, it's normal to have ups and downs and he's feeling the pressure a little bit."

Djokovic's compatriot Ana Ivanovic, who followed his major-winning exploits with the French Open crown this year, is also aiming to put a new name on the women's title winning board at the All England Club in the coming weeks.

It is a daunting prospect for the ever-cheerful new world number one given that several names appearing in the draw also feature on the board.

Defending champion Venus Williams is looking for a fifth title and few would discount her chances or those of her sister twice former champion Serena, given their grasscourt power game and their love of the big stage.

Maria Sharapova, winner in 2004 at the age of 17, took herself away from tennis "to rest body and mind" after a poor showing at the French open and returned keen to restore her number one ranking.

"There's lots of big competitors in the draw, different types of players.Hopefully it will all come together," Sharapova said.

The Russian is seeded to meet second seed Jelena Jankovic in in the semi-finals.